Building materials such as concrete can be reinforced with fibers in order to overcome specific issues that can arise when using conventional reinforcement members, such as steel rebars and/or welded wire mesh. Fibers can introduce toughness (i.e., energy absorption capacity during failure) to concrete, overcoming its intrinsic brittleness and providing post-cracking strength under direct or indirect tensile stresses. The vast majority of conventional fibers used for reinforcing concrete reinforcement are made out of low or high carbon content steel, or polymers such as polypropylene, polyvinyl alcohol, polyester, etc. These conventional fibers suffer from limitations. Processability issues can be generated by the relatively high dosages required (such as clustering during mixing, blockings during pumping, reduction of workability, and difficult compaction and finishing). Additionally, the cost-performance benefit of such conventional fibers is often less than that of traditional solutions due to the relatively high dosages required; durability concerns; health, safety, and environment problems; etc. Composite reinforcing materials, such as composite fibers, can overcome the shortcomings of conventional fibers; i.e., by achieving a very high performance at relatively low dosages.
JP2002154853A1 describes composite fibers produced by impregnating a continuous inorganic fiber bundle with a resin, hardening the resulting material and thereafter cutting the hardened material. The resin content of this composite fiber is 10 to 80 mass %. Its length is 10 to 80 mm and its cross section is 0.1 to 12 mm.
WO2006059041 A1 discloses composite fibers or composite tapes based on co-melted glass fibers and polypropylene fibers, such as the composite products sold under the Twintex® brand (available from Owens Corning) and manufactured by thermoplastic pultrusion.
However, these known composite fibers suffer from the problem of relatively high production costs. Key to production cost is the production rate. For example, JP2002154853A1 describes line speeds of only 5 meters/minute.
Higher production rates can be achieved by using radiation curing technology. U.S. Pat. No. 4,861,621, incorporated herein by reference, discloses a pultrusion process which cures materials by ultraviolet radiation for optic cable applications. Specifically, a reinforcing filamentary material, in the form of a glass roving, is impregnated with a curable coating material and then passed underneath a unit for UV radiation. The pultrusion speed is 10 meters/minute (Example 2).
Other UV curing processes are known in the art. However, there remains a need in the art for solutions for the reinforcement of concrete that overcome the drawbacks mentioned above, particularly solutions that improve the production rate of composite fibers, which will in turn lower the manufacturing costs.